The program of studies of Acquired Immune Deficiency Syndrome (AIDS) including Kaposi's Sarcoma and Opportunistic Infections is designed to extend investigations on (a) etiologic and risk factors for ID and for Kaposi's sarcoma, and (b) possible role of cytomegalovirus in KS and lymphoid cell change, and (c) the pathogenesis of immunodeficiency and the contribution of immune surveillance failure to appearance of Kaposi's sarcoma and other neoplasia, and (d) investigations of therapies for AID and KS. Epidemiological studies are designed to assess the effects in homosexually active males life style and other factors on the immune system and on the gastrointestinal tract. Health care personnel working with AID patients and hemophiliacs as recipients of blood products will be evaluated for possible transfer. Prognostic significance of T subset and immune functional changes will be examined in AID. Human cytomegalovirus (HCMV) will be investigated by nucleic acid hybridization and restriction endonucleases to determine the relationship between components of HCMV and KS. Mechanisms of immune alteration causing (and deriving from) the selective reduction in T helper/inducer population will be related to changes in lymphokine production and receptor appearance with attention to imparied cytotoxic cell development and reduced capacity for immune surveillance against KS and other tumors. Production of lymphokines for therapeutic trials will be developed on the basis of in vitro replacement studies with AID lymphocytes. IL-2 is the focus of initial purification and preparation procedures. A Phase II trial of interferon in AID with Kaposi's sarcoma is proposed as an outgrowth of initial therapeutic experience. Additional efforts to improve immune function through use of thymus derived factors, lymphokines, modifiers of immune response and anti viral agents are under consideration.